De-tuned multiple rfid antenna arrangement for gaming

ABSTRACT

A gaming table contains a number of antennas that are de-tuned from the resonant frequency of a single RFID tag. This increases the power required to read the single tag but matches the resonant frequency for reading a stack of RFID tags. The gaming table may further include a network analyzer and a set of capacitors that are dynamically switched among the antennas according to measuring the reflection coefficient of the antennas.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/587,293 for “De-Tuned Multiple RFID Antenna Arrangement forGaming” filed Jan. 28, 2022, which claims the benefit of U.S.Provisional App. No. 63/283,086 for “De-Tuned Multiple RFID AntennaArrangement for Gaming” filed Nov. 24, 2021, all of which areincorporated herein by reference.

BACKGROUND

The present invention relates to gaming, and in particular, to a radiofrequency identification (RFID) system with an antenna arrangement fordetecting the locations of RFID tags on a gaming table.

Unless otherwise indicated herein, the approaches described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Tracking the location of gaming tokens in real-time on a gaming tablehas the potential to revolutionize the gaming industry by providing cashmanagement and improved security. Tying this data to specific playersallows casinos to create accurate player profiles while simultaneouslyalleviating the pit boss of mundane tasks that take years of training tohone.

Traditional RFID systems have tried to address the gaming market withlimited success. In a typical RFID system, the excitation antennadefines a “working volume” within which the energy projected by theantenna is sufficient to power the RFID tag. This “working volume” isgenerally poorly defined with the only option to increase/decrease powerto adjust the read range. But doing so extends the read range in ALLdirections, introducing cross-talk errors when multiple antennas are inclose proximity. Existing products on the market suffer from multipleshortcomings. First, they are limited to discrete betting spots. Second,they are limited in the chip stack heights they can read. Third, theyhave very poor discrimination between adjacent betting spots. Fourth,they have higher than acceptable read errors. Fifth, they have slow readrates that miss important events (e.g., placement and removal of chips,etc.).

These shortcomings limit the available technology to games where thebetting spots are widely separated (e.g., a single “pot”), to detectinginitial bets only (not capturing transient events such as payouts), andto identifying counterfeit tokens only prior to their use on a table(not during gameplay).

U.S. Application Pub. No. 2013/0233923 discusses a ferrite coretechnology. The ferrite core technology overcomes many of theabove-noted shortcomings, but does not address the need to trackmultiple separate bets placed by different bettors on a single largerbetting spot (such as when “back bettors” share a betting spot withseated bettors on traditional Baccarat layouts). Also needed is theability to discriminate the location of very closely spaced bets (suchas can be found on a roulette table).

U.S. Application Pub. No. 2017/0228630 discusses a solution involvingtwo intersecting antenna arrays. One array of horizontal antennasprovides one coordinate, and a second array of vertical antennasprovides a second coordinate. Signal strength information comparingadjacent antennas may then be used to interpolate a higher fidelity setof coordinates.

Although the approach of U.S. Application Pub. No. 2017/0228630 doeswork, it suffers from the simple fact that reading RFID tags takestime—and reading tags multiple times for purposes of interpolationmultiplies the required time such that capturing an accurate “snapshot”of transient events with large numbers of tags may not be practical incertain gaming environments.

The typical RFID system addresses the question, “Who's there?” Theresponse is a series of unique item identifiers (e.g., serial numbers).As discussed above, the ferrite core technology discussed in U.S.Application Pub. No. 2013/0233923 is directed to addressing theadditional question “Where are you?” as a way to track individual bets.

U.S. Application Pub. No. 2016/0217645 discusses using a networkanalyzer device prior to an RFID read, thereby being able to direct theRFID reader to only those antennas with tags present. This describes aserial approach that eliminates the “overhead” of looking for tags usingan RFID reader where none are present, as using the network analyzerdevice takes less time than using the RFID reader.

Both U.S. Application Pub. No. 2013/0233923 and U.S. Application Pub.No. 2016/0217645 involve the placement of bets in specific areas (thebetting spots). RFID tags not placed in one of the defined areas willnot be read correctly. Neither of these disclosures addresses the needto detect bets placed anywhere on a larger bounded area. The additionaldisclosure of U.S. Application Pub. No. 2017/0228630 does addressplacing multiple bets within a larger bounded area. However, the systemdisclosed therein involved multiple RFID reads to define the coordinatesof each bet, which is a time-consuming process.

All three of U.S. Application Pub. No. 2013/0233923, U.S. ApplicationPub. No. 2016/0217645 and U.S. Application Pub. No. 2017/0228630describe systems to identify and locate RFID tags by using signalstrength information as measured by the RFID reader to determineproximity to a specific antenna. U.S. Application Pub. No. 2013/0233923describes a system that increases the signal strength at the properantenna, which further improves accuracy.

U.S. Application Pub. No. 2021/0011107 discusses various antennaarrangements for gaming.

SUMMARY

One issue with existing systems is that specific gaming tables havespecific betting areas of varying sizes, which makes reading the RFIDtags in each area a challenge. There is a need for antenna arrangementsthat work well with specific gaming tables, such as a roulette table.

Given the above, embodiments are directed toward improving the detectionof RFID tags on a roulette table.

According to an embodiment, a system determines locations of objects ina gaming environment. The system includes a number of radio-frequencyidentification (RFID) antennas arranged at a plurality of locations on agaming table, and an RFID reader coupled to the RFID antennas. Anantenna is impedance matched with a stack of RFID tags with a firstimpedance matching value, where the first impedance matching valuediffers from a second impedance matching value for impedance matchingthe antenna with a single RFID tag. The first impedance matching valueresults in a less efficient impedance matching than the second impedancematching value between the single RFID tag and the antenna.

The system may further include one or more reactive tuning componentsthat couple the antenna to the RFID reader, where the one or morereactive tuning components are selected from capacitors and inductors.The antenna is impedance matched to the stack of RFID tags by adjustinga reactance of the one or more reactive tuning components.

Each of the antennas may be impedance matched with the stack of RFIDtags according to a corresponding type for each of the plurality ofantennas, where the type includes a size, a shape and a configuration.The types of antennas may include a spot antenna type, a line antennatype, and a cross antenna type.

According to an embodiment, a method determines locations of objects ina gaming environment. The method includes providing a number ofradio-frequency identification (RFID) antennas arranged at a number oflocations on a gaming table. The method further includes providing anRFID reader coupled to the plurality of RFID antennas. An antenna isimpedance matched with a stack of RFID tags with a first impedancematching value, where the first impedance matching value differs from asecond impedance matching value for impedance matching the antenna witha single RFID tag. The first impedance matching value results in a lessefficient impedance matching than the second impedance matching valuebetween the single RFID tag and the antenna.

The following detailed description and accompanying drawings provide afurther understanding of the nature and advantages of embodiments of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a roulette table 100.

FIG. 2 is a block diagram of an RFID system 200.

FIG. 3 is a graph 300 of a Smith chart for an antenna tuned for a singleRFID tag.

FIG. 4 is a graph 400 of a Smith chart for an antenna tuned for a stackof 20 RFID tags.

FIG. 5 is a flowchart of a method 500 of determining locations ofobjects in a gaming environment.

FIG. 6 is a block diagram of a RFID system 600.

FIG. 7 is a block diagram of an RFID system 700 that implements adynamic tuning system.

FIG. 8 is a top view of an antenna arrangement 800 that covers an areaon a gaming table.

FIG. 9 is a top view of an antenna arrangement 900 that covers an areaon a gaming table.

FIG. 10 is a top view of an antenna arrangement 1000 that covers an areaon a gaming table.

FIG. 11 is a block diagram of an RFID system 1100.

FIG. 12 is a flowchart of a method 1200 of determining locations ofobjects in a gaming environment.

FIG. 13 is a block diagram of a RFID system 1300.

DETAILED DESCRIPTION

Described herein are techniques for location determination of RFID tags.In the following description, for purposes of explanation, numerousexamples and specific details are set forth in order to provide athorough understanding of the present invention. It will be evident,however, to one skilled in the art that the present invention as definedby the claims may include some or all of the features in these examplesalone or in combination with other features described below, and mayfurther include modifications and equivalents of the features andconcepts described herein.

In the following description, various methods, processes and proceduresare detailed. Although particular steps may be described in a certainorder, such order is mainly for convenience and clarity. A particularstep may be repeated more than once, may occur before or after othersteps (even if those steps are otherwise described in another order),and may occur in parallel with other steps. A second step is required tofollow a first step only when the first step must be completed beforethe second step is begun. Such a situation will be specifically pointedout when not clear from the context.

In this document, the terms “and”, “or” and “and/or” are used. Suchterms are to be read as having an inclusive meaning. For example, “A andB” may mean at least the following: “both A and B”, “at least both A andB”. As another example, “A or B” may mean at least the following: “atleast A”, “at least B”, “both A and B”, “at least both A and B”. Asanother example, “A and/or B” may mean at least the following: “A andB”, “A or B”. When an exclusive-or is intended, such will bespecifically noted (e.g., “either A or B”, “at most one of A and B”).

In this document, the terms “RFID tag”, “RFID gaming tag”, “RFID chip”,“RFID gaming chip”, “gaming chip”, and “gaming token” are used. Suchterms are to be read as being broadly synonymous. (More precisely, an“RFID chip” may be used to refer to the integrated circuit components ofthe “RFID tag”, which also includes additional components such as anantenna, a rigid housing, etc. However, this document is mostlyconcerned with the broad usage for these terms.) The RFID tag respondsto a radio frequency signal from the RFID reader, generally with itsserial number or other identifier, enabling the RFID reader to obtain aninventory of the RFID tags in the vicinity. In a gaming context, theRFID gaming tags may be placed on, removed from, or moved around on agaming table as bets and payouts, according to various game rules. TheRFID gaming tags may be marked with a value identifier (e.g., $1).

Roulette Overview

Roulette is a table game that includes a spinning wheel. Players mayplace bets at various locations on the gaming table that are associatedwith numbers on the wheel, and the bets are paid out based on where aball lands on the wheel. A typical roulette wheel has 36 numbered spots(labeled 1-36) and 1, 2 or 3 “zero” spots (typically labeled 0, 00 and000; for purposes of this document, assume 1 “zero” spot). The numberedspots are also colored, with the “zero” spot colored green, half thespots 1-36 colored red, and the other half colored black. The numbers onthe wheel are typically ordered in a defined non-sequential way.

FIG. 1 is a top view of a roulette table 100. The wheel is omitted. Theroulette table 100 has a number of betting areas in which gaming tokensmay be placed, corresponding to various bets. These betting areasinclude a 3×12 grid of areas labeled 1-36 (corresponding to the 36numbered spots on the wheel), an area labeled 0 (corresponding to the“zero” spot), 3 areas for betting on groups of 12 numbers (1st 12[1-12], 2nd 12 [13-24], 3rd 12 [25-36]), 6 areas for betting on othernumber groups (1-18, 19-36, even, odd, red, black), 3 areas for bettinga specific column of 12 numbers (column 1 that includes the numberedspot for 1, column 2 that includes the spot for 2, column 3 thatincludes the spot for 3), and a “racetrack” that includes each of thenumbers on the wheel and 4 areas for other bets (series 5/8, orphelins,series 0/2/3, 0-game). The racetrack is an oval-shaped collection of 37areas that correspond to the 37 numbers on the roulette wheel arrangedas they are on the wheel; this allows for betting on adjacent numbers asthey appear on the wheel, referred to as “neighbors bets”. (Note thatthe figure omits showing the specific number arrangement.) In additionto being able to place bets on adjacent numbers, there are 4 areas ofthe racetrack that allow the bettor to choose specific groups ofnumbers. The series 5/8 bet, also referred to as tiers du cylinder,corresponds to the following 12 numbers: 27, 13, 36, 11, 30, 8, 23, 10,5, 24, 16, 33. The orphelins bet corresponds to the following 8 numbers:17, 34, 6, 1, 20, 14, 31, 9. The series 0/2/3 bet, also referred to asvoisins du zero, corresponds to the following 10 numbers: 19, 4, 21, 2,25, 22, 18, 29, 7, 28. The 0-game bet corresponds to the following 7numbers: 12, 35, 3, 28, 0, 32, 15. The types of bets, and thecorresponding betting spots on the roulette table, may be varied fromthose shown on the roulette table 100 as desired.

Bets can be made in various ways: a single number (by placing a gamingtoken within a betting area, e.g. the area for the number 12), a pair ofnumbers (placed on the line between two numbers, e.g. 11, 14), 3 numbersin a specific row (placed on the line at the edge of the row, e.g. 13,14, 15), 4 numbers that share an intersection (placed at theintersection, e.g. 5, 6, 8, 9), 6 numbers in two adjacent rows (placedon the line at the edge of the two rows at the intersection, e.g. 22,23, 24, 25, 26, 27), 12 numbers in a column (placed in the column area),or within one or more of the other betting areas (e.g. the groups of 12,the groups of 18, odd, even, red, black, the racetrack areas, etc.).

Each of these bets has different odds and therefore different payouts,which can range from 35:1 to 2:1. The current state of the art requiresthe croupier to identify all winning combinations and correctly sum upthe proper payout for each player. For example, a single player may getpaid out with a formula such as: 2*35+3*17+5*11+10*2=196. It is not hardto imagine errors occurring. With a house advantage of 3%, it does nottake many errors to have a negative impact on casino profitability.

Roulette differs from other casino games in that it uses dedicated“color” chips—one color for each player—instead of the “value” chipsused in other casino games (e.g., $1 chips, $25 chips, etc.). When aplayer wants to bet at a roulette table, they must first exchange theirvalue chips for color chips. When doing so, each player must declare thecorresponding value of their color chips. All chips of one color havethe same value, and other colors may have different values. For example,Player 1 may select blue chips and declare their value to be $1 each,Player 2 may select red chips declared at $5 each, and Player 3 mayselect white chips and declare their value to be $100 each. In manycasinos, this is done verbally and it is up to the croupier to managethese exchanges.

Casinos have a long history of rewarding their best customers. Theserewards are referred to as “comps” and can take the form of meals,lodging, extra chips, drinks, etc. The value of the comps are tied tothe volume of play, with longer play and higher bets inevitablyresulting in more revenue for the house. Thus it is important toaccurately track the betting volume and bet type of each player. (Inthis context, the bet type may be one of a number bet, a row bet, acolumn bet, an odd/even bet, etc. and is identified and tracked usingRFID tags because each bet type has different odds.) To do thisaccurately, it is important to tie each bet to its corresponding bettor.In roulette, the use of unique color chips for each player makes thisfeasible. When a player “buys in” to a roulette table, they exchangecash or value chips for color chips. Having the player also use anRFID-enabled loyalty card (or equivalent) to insure proper comps arereceived is beneficial to all parties. Furthermore, tracking theplayer's win/loss ratio throughout their tenure at the roulette tablewill result in a more accurate picture of player behavior.

Each game of roulette involves spinning the roulette wheel, and thewinning number is determined by where the ball lands within the spinningwheel. At this point, the croupier places a “dolly” on the correspondingnumber on the table top. The dolly remains in place until all losingbets are removed and all winning bets are paid out. Due to thecomplexity of the number and types of bets, the dolly aids in resolvingmis-understandings between house and player. In addition, tables areknown to become “unbalanced” (uneven statistical outcomes). For example,the table may become unbalanced due to worn bearings on the wheel,mounting the wheel at a slight incline, physical wear on the wheel suchas worn edges on the bumpers separating each of the pockets where theball lands, etc. Detection can be achieved by studying the statisticalvariability of the ball landing on a specific spot (as compared to thedesired case where all spots have an equal probability).

A game of roulette may be defined using three states: Open Betting,Play, and Payout. In the Open Betting state, the wheel is spun, the ballis released, and players may freely place and remove bets. The OpenBetting state is initiated by the new game event and ends with the betslocked event, while the ball is still in motion in the wheel. The OpenBetting state is followed by the Play state. The Play state is initiatedby the bets locked event and ends with the winning number event. In thePlay state, the ball is still in motion but players may not place orremove bets; the winning number event occurs when the ball stops in anumbered pocket on the wheel. The Play state is followed by the Payoutstate, which is initiated by the winning number event and ends with theend of game event. In the Payout state, the croupier removes losing betsand pays out winning bets. The system then transitions from the current(completed) game to the subsequent (next) game and a new set of OpenBetting, Play and Payout states.

As discussed in more detail in the Payout Calculator section, the systemmay monitor a number of potential events, including tracking individualbets on each betting spot, identifying late or changed bets (referred toas “capped” bets), tracking the removal of both losing and winning bets,and tracking of “let it ride” bets for the subsequent game.

Prior to the bets locked event, players are free to place new bets orchange existing bets. Once the bets locked milestone is reached, placingnew bets is not allowed and the system may detect any new bets orchanges in existing bets and generate an alert. The bets locked eventcan be automated (e.g. sensors in the wheel, voice command from thecroupier, etc.) or determined manually (e.g. pressing a switch).Similarly, the winning number event can be automated (e.g. sensors inthe wheel, voice command) or determined manually (e.g. placement of anRFID-enabled dolly on the antenna for the winning number; see theInstrumented Dolly section below). Similarly, the end of game event canbe automated (e.g. removal of the RFID-enabled dolly from the antennafor the winning number; see the Instrumented Dolly section below) ordetermined manually (e.g. a “change of game state” switch).

RFID Tags and Roulette

Previous disclosures, including U.S. Application Pub. Nos. 2013/0233923and 2017/0228630, discuss the detection of RFID-enabled gaming tokens byantennas on a gaming table. However, roulette presents some specificchallenges that cannot be addressed solely by these earlier disclosures.First, the spacing of adjacent betting spots on roulette issignificantly tighter and is constrained by defined table geometries.Second, player behavior results is significantly taller stacks of chipsplaced on one or more spots, necessitating increased sensitivity andspecificity when assigning chips to specific betting spots. Third, thereis a wide variety of shapes and sizes for the betting spots.

In general, a RFID tag is tuned to a specific resonant frequency, e.g.13.56 MHz. The traditional solution is to configure the RFID tag with ahigh, narrow Q at the resonant frequency, in order to reduce the amountof power that must be output by the RFID reader in order to generate aresponse by the RFID tag. In contrast to this traditional solution, U.S.Application Pub. No. 2013/0233923 describes using a ferrite core andcomponents that tunes the RFID tag to a frequency higher than 13.56 MHz.Any coupling by adjacent RFID tags shifts their resonant frequency lowerand thus closer to 13.56 MHz, increasing the power received from theRFID reader. In summary, U.S. Application Pub. No. 2013/0233923describes tuning the Q of the RFID tag.

In response to these challenges, the following sections describe anumber of features that improve the detection of RFID tags on a roulettetable. First, the Antenna Tuning section and the Dynamic Antenna Tuningsection (Sections 1 and 2 below) describe tuning the excitation tag ofthe RFID reader to further increase the read range as defined by theheight of a stack of RFID tags placed on an antenna. Note that thesesections differ from the tuning described in U.S. Application Pub. No.2013/0233923 in that they are directed toward tuning the antenna in theRFID reader, not tuning the antenna in the RFID tags.

Second, the Fast Scanning of Antennas section (Section 3 below)describes using the antenna reflection coefficient S11 for antennas withlarger areas than as described in previous disclosures such as U.S.Application Pub. No. 2016/0217645.

Third, the Instrumented Dolly section (Section 4 below) describesfeatures for improving the transitions between game states in roulette.

As a result, the features described herein enable a number ofimprovements in data collection, monitoring, and process control tosupport casino operations for roulette. First, they enable correctlydetecting the number and color of each chip on a betting spot, correctlydistinguishing the bets on one spot from any bets on adjacent spots, andcorrectly tracking the total bets placed for each spin of the wheel.Second, they enable clearly defining game state in order to adjust gamelogic using an RFID-enabled dolly, correctly identifying the winningnumber, and correctly calculating the payout for each bet and displayingthis information in an easy to use format. Third, they provide a set ofalarms tailored to detecting illegal chip movements in roulette. Fourth,the assist in unambiguously assigning the value of each chip color.Fifth, they enable tracking the betting habits of individual players,tracking dealer metrics (e.g. speed of play, number and type of errors,etc.), tracking game outcomes over time to determine if the wheel is“true”, and automatically Open/Close a table (e.g. during personnelshift changes).

1. Antenna Tuning

FIG. 2 is a block diagram of an RFID system 200. The RFID system 200 maygenerally be implemented in a gaming table, specifically a roulettetable, that includes features such as betting spots similar to thoseshown in FIG. 1 , a wheel, etc. The RFID system 200 includes acontroller 202, an RFID reader 204, a multiplexers 206, and a number ofantennas 208.

The controller 202 generally controls the operation of the RFID system200. The controller 202 controls the RFID reader 204 to generate a readcommand and receives the RFID tag identifiers from the RFID reader 204in response to the read command. The controller 202 controls themultiplexer 206 to connect to a selected one of the antennas 208. Thecontroller 202 includes a tag database that associates RFID tagidentifiers with chip values. The controller 202 may also implementother functionality, such as calculating and displaying chip valuescorresponding to the detected RFID tag identifiers, tracking gamestates, generating alerts, etc. as described throughout this document.The controller 202 may be implemented by a computer or other device thatincludes a processor, such as a personal computer.

The RFID reader 204 generates a read command by outputting a carrierwave at a given frequency; any RFID tags that receive the power respondwith their tag identifier by modulating the carrier wave. The RFID tagsmay respond according to an anti-collision process. The RFID tags mayalso be responsive to an acknowledgement command from the RFID reader204, so that a given tag stops responding until the next read cycle.

The multiplexer 206 connects the RFID reader 204 to a selected one ofthe antennas 208. The multiplexer 206 may be implemented with radiofrequency switches. In response to a command from the controller 202,the multiplexer 206 connects a selected antenna 208 to the RFID reader204. This enables multiple antennas to be associated with one RFIDreader. The RFID reader 204 then selectively connects to the antennas208 in a time share manner.

The antennas 208 are generally associated with areas on the roulettetable. For example, a given antenna 208 may be associated with thebetting spot for betting on the number “1”. In addition, roulette betsmay be placed on the lines and intersections between multiple numberedspots, and antennas may be associated with these lines andintersections. As these betting spots, lines and intersections havedifferent sizes and shapes, the sizes and shapes of the antennas 208 mayvary as well, as discussed in subsequent paragraphs.

As a specific example for a roulette table, the RFID system 200 includes200 or more antennas 208 on multiple printed circuit boards feeding intoa single RFID reader 204. Embodiments with multiple readers andmultiplexers (e.g. one reader and one multiplexer per circuit board) mayalso be implemented, with the controller 202 coordinating the multipleRFID readers and multiplexers. With the RFID reader 204 taking anaverage of 5 msec to perform a read, this arrangement results in theRFID reader 204 taking 1 second to read all 200 of its associated set ofthe antennas 208 if no tags are present; reading a tag takesapproximately 7 msec, so if 50 tags are present, the total read time is1.35 seconds (5 msec*200+7 msec*50). The number of RFID readers 204, thenumber of multiplexers 206, and the number of antennas 208 may beadjusted as desired.

As discussed above, roulette has unique requirements that strain thesensitivity and specificity of reading closely-spaced RFID tags. UsingRFID tags with a ferrite core (e.g. as described in U.S. ApplicationPub. No. 2013/0233923), the RFID tags are very tightly coupled andmultiple tags can detune from the proper antenna match.

In contrast to what would be expected in a conventional RFID system(e.g., in which the antenna is tuned to the resonant frequency of theRFID tags), the RFID system 200 is somewhat counter-intuitive in thatthe antennas 208 are not tuned to the typical resonant frequency of theRFID tags. Instead, the antennas 208 are de-tuned in a manner that istailored such that the resulting frequency shift that occurs whenmultiple tags are present moves in the direction of optimal tuning,while still retaining the requisite sensitivity when only a small numberof RFID tags are present in the radio frequency excitation field. Inthis manner, any diminution of signal strength from chips added to thetop of a stack on a betting spot (due to distance from the excitationantenna) is offset by increased sensitivity as the resonance shiftscloser to the ideal.

Careful measurement of the coupling as a function of the number of chipsin the stack allows configuring each of the antennas 208 with a tuningto maximize the sensitivity of the antenna (and thereby maximizing theheight of the stack of chips that can be read at a given power level).

To get the highest field strength it is desirable to have a high Q. Thetradeoff is that a high Q circuit is easily detuned—and placement ofmultiple chips in the excitation field will cause this de-tuning. Thuswith high Q antennas, it is best to tune for a high stack height. Tuningto the tall stack height (rather than for a single chip) can result in 7dB signal improvement at the top of the stack (where the excitationfield is weakest). As a result, system performance limits are set by thechip on the top of the stack.

FIG. 3 is a graph 300 of a Smith chart for an antenna tuned for a singleRFID tag. The scaling is omitted, and the antenna is tuned for 50 Ohms.The graph 300 includes 4 data points corresponding to the reflectioncoefficient S11 measured for various numbers of RFID tags arranged in astack on the antenna. Point 302 corresponds to 1 tag, point 304corresponds to 5 tags, point 306 corresponds to 10 tags, and point 308corresponds to 20 tags. Because the antenna is tuned for 1 tag, point302 lies near the center of the chart, indicating a close impedancematch to 50 Ohms. Points 304, 306 and 308 are all the way at the rightedge, indicating a large impedance mis-match, which occurs when only afew more tags are added to the stack. As a result of the impedancemis-match, a much higher power level is required to perform a read.Thus, tuning the antenna for a single tag severely limits thesensitivity (e.g. ability to read larger numbers of tags) at a givenpower level.

FIG. 4 is a graph 400 of a Smith chart for an antenna tuned for a stackof 20 RFID tags. The scaling is omitted, and the antenna is tuned for 50Ohms. The graph 400 includes 4 data points corresponding to thereflection coefficient S11 measured for various numbers of RFID tagsarranged in a stack on the antenna. Point 402 corresponds to 1 tag,point 404 corresponds to 5 tags, point 406 corresponds to 10 tags, andpoint 408 corresponds to 20 tags. Because the antenna is tuned for 20tags, point 408 lies in the center of the chart, indicating a closeimpedance match. Points 402, 404 and 406 are a bit offset from thecenter, but not as far offset as in FIG. 3 , indicating less of animpedance mis-match than in FIG. 3 . It is important to note that whilethe impedance match is degraded when fewer chips are present, theyrequire less power than the mis-match of FIG. 3 and therefore can stillbe read in spite of the mismatch.

TABLE 1 shows a comparison of tuning between 1 tag and 30 tags for a4-turn loop antenna with a diameter of 30 mm.

TABLE 1 When reading 1 tag When reading 30 tags Reactance Power PowerTuning Series Shunt Impedance required Impedance required  1 tag 162 pF936 pF 52 + j3 Ω  0.5 mW  5 − j9 Ω 603 mW 30 tags 194 pF 226 pF  4 + j38Ω 1.55 mW 48 + j2 Ω 115 mW

In TABLE 1, the “Tuning” column indicates the two options beingcompared, namely 1 tag versus 30 tags. The “Reactance” column indicatesthe corresponding reactance of the reactive components coupled to theantenna in order to perform impedance matching for the indicated numberof tags. Here, the reactive components are a series capacitor (e.g., acapacitor in a series connection between the RFID reader and theantenna) and a shunt capacitor (e.g., a capacitor in a shunt connectionbetween the RFID reader and the antenna). The specific reactance of thereactive components coupled to the antenna may be determined bymeasurement during system configuration, as further discussed below. The“When reading 1 tag” columns indicate the impedance and power requiredto read 1 tag, based on whether the antenna is tuned for 1 tag or 30tags. The “When reading 30 tags” columns indicate the impedance andpower required to read 30 tags, based on whether the antenna is tunedfor 1 tag or 30 tags.

As can be seen, when the antenna is tuned for 1 tag, the selectedcapacitance values result in an impedance of 52+j3 Ohms, which is a goodimpedance match to the 50 Ohm impedance of the RFID reader. As a result,only 0.5 mW is required to perform the read. However, when a stack of 30tags is placed on this antenna, the impedance changes dramatically to5-j9 Ohms and to read all 30 chips requires 603 mW of power, due to theimpedance mismatch with the RFID reader.

By comparison, when the antenna is tuned for 30 tags, the selectedcapacitance values result in an impedance of 48+j2 Ohms, which is a goodimpedance match to the 50 Ohm impedance of the RFID reader. As a result,only 115 mW of power is required to perform the read, which is animprovement of 7.2 dB in efficiency (versus the 603 mW of the othertuning). Admittedly, tuning the antenna in this manner does require 3times more power to read the single chip, but this inefficiency is veryacceptable at just 1.55 mW.

In other words, by tuning the antenna to match the impedance for a stackof RFID tags, the required minimum power is increased (e.g. 0.5 to 1.55mW) and the required maximum power is decreased (e.g. 603 to 115 mW).Although the power efficiency is reduced by a small amount (e.g.approximately 1 mW) when reading the single tag, it is improved by alarge amount (e.g. approximately 490 mW) when reading larger number oftags. As a result, the overall power efficiency of the system isimproved.

TABLE 2 shows various antenna types that may be used on a roulettetable, such as the roulette table 100 (see FIG. 1 ).

TABLE 2 Betting area Size (mm) Shape Configuration Turns Main numberspot 47 × 70  Rectangular Loop 3 Horizontal line 29 × 70  RectangularLoop 3 Cross 28 × 28  Rectangular Loop 5 Vertical line 28 × 47 Rectangular Loop 4 Column 70 × 90  Rectangular Dual FIG. 8 2 Group of 1268 × 325 Rectangular Dual FIG. 8 1 Red/Black 90 × 180 Rectangular DualFIG. 8 2 Racetrack number spot 30 Circular Loop 4 Internal racetrack A42 × 180 Rectangular Dual FIG. 8 2 Internal racetrack B 42 × 160Rectangular Dual FIG. 8 2

In TABLE 2, each antenna type is associated with a betting area and hasa size, a shape, a configuration, and a number of turns.

The “Betting area” column indicates the type of betting area on theroulette table, as follows. The main number spot area is associated witheach of the 36 numbered betting areas in the 3×12 grid. The horizontalline area is associated with the horizontal line between two of the 36numbered betting areas, for placing a bet on both numbers (e.g. 5, 8).The cross area is associated with the intersection between four of the36 numbered betting areas, for placing a bet on all 4 numbers (e.g. 5,6, 8, 9). The vertical line area is associated with the vertical linebetween two of the 36 numbered betting areas, for placing a bet on bothnumbers (e.g. 5, 6). The column area is associated with each column of 3numbers, for placing a bet on all 3 numbers (e.g. 13, 14, 15). The groupof 12 area is associated with each of the 3 areas labeled “1st 12”, “2nd12” and “3rd 12”. The red/black area is associated with each of the 6areas labeled “red”, “black”, “1-18”, “19-36”, “even” and “odd”. Theracetrack number spot is associated with each of the 37 numbered bettingareas surrounding the racetrack area. The internal racetrack A and B areassociated with each of the 4 areas within the racetrack area labeled“Series 5/8”, “Orphelins”, “Series 0/2/3” and “0-Game”, with the A areaassociated with the larger two areas and the B area associated with thesmaller two areas.

The “Size” column indicates the size of the antenna. The “Shape” columnindicates the shape of the antenna. The “Configuration” indicateswhether the antenna is configured as a loop or as a figure-8. A figure-8antenna has two loops, with the antenna wire crossing in the middlebetween the loops; as a result, the field in one loop has a 180 degreephase shift from the field in the other loop. A dual figure-8 antennahas two figure-8 antennas offset so that the second figure-8 covers thenull zone between the two loops of the first figure-8 antenna. The“Turns” column indicates the number of turns that the antenna has. Asingle turn may be visualized for a circular antenna as the antenna wireturning 360 degrees, two turns correspond to 720 degrees, three turnscorrespond to 1080 degrees, four turns correspond to 1440 degrees, etc.All of these parameters affect the values of the reactance componentscoupled to each antenna for impedance matching.

More generally, the antenna types of TABLE 2 may be categorized intothree general types: Spot, line and cross. The spot type generallycovers an area, for example corresponding to a given betting spot. Theline type generally covers a border between two betting areas, forexample corresponding to a bet on both of those numbers. The cross typegenerally covers the intersection between four betting areas, forexample corresponding to a bet on all four of those numbers. The numberof betting spots, their arrangement and sizes, etc. may be adjusted asdesired, with corresponding adjustment to the size, shape, configurationand number of turns for the associated antenna.

Once the antenna types have been selected, reactance circuits for eachantenna may be configured to match impedance for a stack of tags. Forexample, as discussed above with reference to TABLE 1, the racetracknumber spot antenna (see also TABLE 2) has a size of 30 mm, a circularshape, a loop configuration and 4 turns; when tuned to impedance matchfor 30 tags, the corresponding reactance circuits include a seriescapacitor at 194 pF and a shunt capacitor at 226 pF. The other antennason the roulette table 100 may be tuned in a similar manner. For example,the impedance may be measured for a stack of 30 tags, and the reactanceof the reactance circuits (e.g., one or more of capacitors and inductorsin one or more of series and shunt configurations) may be adjusted untila reasonable match is achieved. A network analyzer device may be used toperform the impedance matching, for example by measuring the reflectioncoefficient and adjusting the reactance in response to the measurement.

TABLE 3 provides an example of the tunings for three of the antennatypes shown in TABLE 2 to match a stack of 30 RFID tags.

TABLE 3 Tuning for reactive components Type Series capacitor Shuntcapacitor Circular 30 mm loop with 4 turns 194 pF 226 pF Circular 90 mmloop with 2 turns 220 pF 750 pF Rectangular 29 × 70 mm  54 pF 120 pFloop with 3 turns

In TABLE 3, it can be seen how the reactance values of the reactivecomponents vary based on the type of antenna.

FIG. 5 is a flowchart of a method 500 of determining locations ofobjects in a gaming environment. The method 500 may be performed on theroulette table 100 (see FIG. 1 ) using the RFID system 200 (see FIG. 2).

At 502, a number of radio-frequency identification (RFID) antennasarranged at a plurality of locations on a gaming table are provided. Forexample, the antennas may have the various types listed in TABLE 2 andmay be arranged in the betting areas of the roulette table 100 asdiscussed above.

At 504, an RFID reader coupled to the RFID antennas is provided. Forexample, the RFID system 200 may be integrated into the roulette table100, and the RFID system 200 may include one or more RFID readers 204that are coupled to the RFID antennas on the roulette table 100.

As discussed above, each of the antennas is impedance matched with astack of RFID tags with a first impedance matching value, where thefirst impedance matching value differs from a second impedance matchingvalue for impedance matching the antenna with a single RFID tag. Forexample, TABLE 1 shows that the first impedance matching value is 48+j2Ohms and the second impedance matching value is 52+j3 Ohms, resultingfrom the configuration of the reactive elements. As a result, the firstimpedance matching value results in a less efficient impedance matchingthan the second impedance matching value between the single RFID tag andthe antenna. For example, TABLE 1 shows that when the reactivecomponents are configured to match for tuning 30 tags, the powerrequired is 1.55 mW, which is greater than the 0.5 mW required when thereactive tuning components are configured to match for tuning 1 tag.

At 506, a given antenna of the plurality of antennas is selectivelyconnected to the RFID reader. For example, the controller 202 maycontrol one of the multiplexers 206 to selectively connect one of theRFID readers 204 to one of the antennas 208.

At 508, the given antenna is energized with the RFID reader, whereenergizing the given antenna includes reading a subset of the pluralityof RFID tags. For example, the controller 202 may instruct the givenRFID reader 204 to perform a read of the given antenna 208 (see 506);the controller 202 then associates the tag identifiers resulting fromthe read with the betting spot corresponding to the given antenna.

The RFID system 200 may then perform the method 500 on other of theantennas on the roulette table 100. In this manner, the RFID system 200can determine the amount of bets placed at the various locations on theroulette table 100.

2. Dynamic Antenna Tuning

The antenna tuning system described above in Section 1 works well, butsensitivity is limited by an inherent conflict resulting from a fixedtuning circuit. Specifically, the antenna tuning described in Section 1shifts the antenna matching to be biased for taller stacks of tags, withthe resulting increase in power and inefficiency when reading smallernumbers of tags. The RFID systems described in Section 2 address theseissues.

FIG. 6 is a block diagram of a RFID system 600. The RFID system 600 maybe integrated into a roulette table (e.g. the roulette table 100 of FIG.1 ), in a manner similar to that described above regarding the RFIDsystem 200 (see FIG. 2 ). The RFID system 600 includes a controller 602,a network analyzer 604, an RFID reader 606, a reactance network 608, amultiplexer 610, and antennas 612.

The controller 602 generally controls the operation of the RFID system600. The controller 602 sends commands to the other components of theRFID system 600 and receives data from the other components in responseto the commands. The controller 602 may store a RFID tag database thatcontains the RFID tag identifiers of the RFID tags in use at theroulette table. The controller 602 may manage game states and variousevents of the roulette game. The controller 602 may be implemented by apersonal computer or other device that includes a processor. Thecontroller 602 may be otherwise similar to the controller 202 (see FIG.2 ).

The network analyzer 604 generally measures a reflection coefficient S11of a selected one of the antennas 612. The reflection coefficient, alsoreferred to as the reflectance, is a parameter that describes how muchof a wave is reflected by an impedance discontinuity in the transmissionmedium, in this case a selected one of the antennas 612. The reflectioncoefficient is the ratio of the complex amplitude of the reflected waveto that of the incident wave. The network analyzer 604 may measure thereflection coefficient in a manner similar to that described in U.S.Application Pub. No. 2016/0217645.

The RFID reader 606 generally outputs a read command, which includesenergizing a selected one of the antennas 612 and receiving responsesfrom the RFID tags energized by the field. The RFID reader 606 may beotherwise similar to the RFID reader 204 (see FIG. 2 ).

The reactance network 608 generally includes a number of reactiveelements, including capacitors, inductors, etc. that may be connected invarious configurations, including in series configurations, in shuntconfigurations, etc. The reactance network 608 is responsive to acommand from the controller 602 that selects a particular set ofreactive elements and their configuration to result in a particularreactance. The reactance network 608 may include specific configurationsof elements where a particular configuration is selected. For example,when there are 10 types of antennas that can each be tuned to 5different stack heights (e.g. 30, 20, 10, 5, 1), the reactance networkmay include 50 configurations of reactive elements. Alternatively, thereactance network 608 may include a first configurable set of reactiveelements that may be connected in a series configuration, and a secondconfigurable set of reactive elements that may be connected in a shuntconfiguration. For example, the first set may include four seriescapacitors with sizes of 200, 100, 50 and 25 pF; selecting one or more(or selecting none) results in a series capacitance that is selectablefrom 0 to 375 pF in 25 pF increments.

The multiplexer 610 selectively connects the reactive network 608 to oneof the antennas 612 in response to a command from the controller 602.The selected antenna 612 then connects via the reactive network 608(having a selected configuration) to the network analyzer 604 to measurethe reflection coefficient of the selected antenna, or to the RFIDreader 606 to read the RFID tags in the vicinity of the selectedantenna.

The antennas 612 are located on various locations on the roulette table100, similar to that described above regarding the antennas 208 (seeFIG. 2 ). The antennas 612 have various types, such that those detailedabove in TABLE 2.

The RFID system 600 may include multiple RFID readers, multiplereactance networks, and multiple multiplexers, where each RFID reader isassociated with one of the reactance networks, one of the multiplexers,and one set of the antennas. This allows the controller 602 to controlmultiple RFID readers to perform read operations at overlapping times.

The RFID system 600 may be used to implement a dynamic tuning system, asdiscussed below.

2.1 Dynamic Tuning System

When configured to implement a dynamic tuning system, the RFID system600 generally operates as follows. The controller 602 first measures thereflection coefficient S11 of a given antenna 612 using the networkanalyzer 604 and then adjusts the tuning of the reactance network 608 toproperly match the given antenna 612. Because the RFID system 600 isdynamically tuning the given antenna 612, it may use antennas with highQ with the resonance tuning adjusted to best match the operatingfrequency, e.g. 13.56 MHz, irrespective of whether there is only 1 tagor multiple tags in the excitation field. Then the controller 602instructs the RFID reader 204—which is selectively connected to thegiven antenna 612 by way of the multiplexer 610—to excite the givenantenna 612 using the selected tuning for optimal performance.

Alternatively, the dynamic tuning system may be implemented without anetwork analyzer, as detailed regarding FIG. 7 .

FIG. 7 is a block diagram of an RFID system 700 that implements adynamic tuning system. The RFID system 700 includes an RFID reader 702,a dual directional coupler 704, a controller 706, a series reactancenetwork 708 a, a shunt reactance network 708 b, a multiplexer 710, andantennas 712.

The RFID reader 702 performs a read operation, including energizing aselected one of the antennas 712 and receiving responses from RFID tagsnear the selected antenna. The RFID reader 702 may be otherwise similarto the RFID reader 204 (see FIG. 2 ), the RFID reader 606 (see FIG. 6 ),etc.

The dual directional coupler 704 taps off the energy of the excitationsignal and the energy of the return signal during the read operation.The dual directional coupler 704 receives the excitation energy from theRFID reader 702, provides the excitation energy to the reactancenetworks 708 a and 708 b, and provides a forward signal 705 a to thecontroller 706. The dual directional coupler 704 receives the responsesfrom the RFID tags, provides them to the RFID reader 702, and provides areflected signal 705 b to the controller 706.

The controller 706 receives the forward signal 705 a and the reflectedsignal 705 b from the dual directional coupler 704 and measures thereflection coefficient based on the forward signal 705 a and thereflected signal 705 b. Based on the reflection coefficient, thecontroller 706 controls the reactance networks 708 a and 708 b to adjustthe series reactance and the shunt reactance. The controller 706 maythen instruct the RFID reader 702 to perform another read operation thatuses the adjusted reactance values.

The series reactance network 708 a couples the RFID reader 702 to aselected one of the antennas in a series configuration of reactiveelements, and the shunt reactance network 708 b couples the RFID readerto the selected antenna in a shunt configuration of reactive elements.The reactance networks 708 a and 708 b each include a number of reactiveelements, including capacitors, inductors, etc. The reactance networks708 a and 708 b may include elements having different reactance values,and the controller 706 may select one or more in order to obtain adesired reactance value. For example, the series reactance network 708 amay include four capacitors with values of 200, 100, 50 and 25 pF; thisallows the selection of any capacitance value from 0 to 375 pF in 25 pFincrements. The shunt reactance network 708 b may include 5 capacitorswith values of 400, 200, 100, 50 and 25 pF; this allows the selection ofany capacitance value from 0 to 775 pF in 25 pF increments. As a result,the reactance networks 708 a and 708 b can selectively provide anappropriate reactance for any of the antennas on the roulette table(see, e.g., the antenna types listed in TABLE 2).

The multiplexer 710 couples the reactance networks 708 a and 708 b to aselected one of the antennas 712, as selected by the controller 706. Inthis manner, the selected antenna 712 is coupled to the RFID reader 702via the reactance networks 708 a and 708 b. The multiplexer 710 may beimplemented by a radio frequency switch.

The antennas 712 are associated with various locations on the roulettetable (e.g., the betting areas discussed above regarding the roulettetable 100 of FIG. 1 ). The antennas 712 come in a variety of types, suchas the types listed in TABLE 2, and quantities. The antennas 712 may beotherwise similar to the antennas 208 (see FIG. 2 ), 612 (see FIG. 6 ),etc.

As compared to the RFID system 600 (see FIG. 6 ), note that the RFIDsystem 700 omits a network analyzer. Instead, the RFID system 700 mayperform one or more additional reads if the current read results in asuboptimal return signal, as determined by the controller 706 byanalysis of the forward and reflected signals.

2.2 Selective Tuning Network

Alternatively, the RFID system 700 may implement a selective tuningnetwork by replacing the reactance networks 708 a and 708 b withspecifically configured selections of series and shunt reactanceelements. For example, the antennas 712 may include 10 different typesof antennas (e.g., the types listed in TABLE 2). A given antenna typehas a number of matching reactance configurations that correspond tovarious RFID tag stack heights. For example, a given antenna may have 5matching reactance configurations corresponding to 5 stack heights (e.g.30, 20, 10, 5, 1). As a specific example for the circular 30 mm loopantenna with 4 turns (see TABLE 3), the tuning for a stack of 30 RFIDtags is a series capacitance of 194 pF and a shunt capacitance of 226pF. This antenna then has four other pre-configured reactanceconfigurations corresponding to 20, 10, 5 and 1 RFID tag. Thus, for 10antenna types and 5 stack heights, the selective tuning network includes50 selectable configurations of reactance elements. When the first RFIDread operation on an antenna results in a mis-match, the controller 706selects another of the pre-configured reactance configurations for thatantenna.

In summary, the dynamic antenna tuning of Section 2 enables a number ofdifferences from the antenna tuning of Section 1. First, dynamic antennatuning enables the use of antennas with a higher Q, which results in anincreased field strength (for a given power level) and the ability toread taller stacks of RFID tags. Second, dynamic antenna tuning enablesthe use of a reactance network that is shared among multiple antennas,instead of each antenna having its own, separate reactanceconfiguration.

These features enable a number of improvements from existing systems.First, they allow the tuning of the resonance of a given antenna to bedynamically changed to match the sensitivity of the given antenna, whichimproves the efficiency of the system (e.g., power savings of theexcitation field generated by the RFID reader). Second, they allow thetuning of the resonance of the RFID reader to be dynamically changedaccording to the differing resonances of antennas that have differenttypes (e.g., different sizes, different shapes, different numbers ofturns, etc.). Third, they allow the tuning of a given antenna to bedynamically changed as different numbers of RFID tags are placed withinthe magnetic field (also referred to as the H field) generated by thegiven antenna when energized.

3. Fast Scanning of Antennas

U.S. Application Pub. No. 2016/0217645 discusses using a networkanalyzer device to measure the change in reflection coefficient S11 ofan antenna in the presence of different numbers of RFID tags. However,the systems described in U.S. Application Pub. No. 2016/0217645 have anumber of issues. One issue is that the systems described in U.S.Application Pub. No. 2016/0217645 do not work well for larger antennas.This issue is problematic for roulette, where some betting spots have alarger area. Increasing the size of the antenna does not work well,because the larger antenna results in a diminished flux density whichreduces the change in S11 such that the presence of RFID tags isdifficult to detect. TABLE 4 gives an example of attempting to measureS11 with a larger antenna.

TABLE 4 Number Reflection of tags coefficient S11 0 (47.6 + j1.8) Ω 1(47.7 + j1.4) Ω 2 (47.7 + j1.2) Ω 3 (47.8 + j0.7) Ω

In TABLE 4, the reflection coefficient S11 is measured for four tagquantities using a 13×30 cm loop antenna matched to 50 Ohms at anexcitation frequency of 13.56 MHz. As can be seen, the measurements arevery close together, making it difficult to distinguish between 0-3tags.

To address these issues, Section 3 describes using multiple antennas todetect RFID tags spread over a larger area. Using multiple antennaskeeps the flux density high enough to ensure a measurable change in S11.The multiple antennas may be configured as loops, as overlapping loops,as figure-8 antennas, as overlapping figure-8 antennas, etc. TABLE 5gives an example of measuring S11 with a figure-8 antenna.

TABLE 5 Number Reflection of tags coefficient S11 0 (36.1 + j6.5) Ω 1(37.7 + j4.4) Ω 2 (39.8 + j0.7) Ω 3 (41.1 − j6.7) Ω

In TABLE 5, the reflection coefficient S11 is measured for four tagquantities using a 7×24 cm figure-8 antenna matched to 50 Ohms at anexcitation frequency of 13.56 MHz. As can be seen, the differences amongthe measurements are greater than those in TABLE 4, making it easier todistinguish between 0-3 tags.

The 13×30 cm area of the 13×30 cm loop antenna may then be covered bymultiple 7×24 cm figure-8 antennas (e.g., using 4 figure-8 antennas).This allows the network analyzer, which returns results much faster thanthe RFID reader, to perform a fast scan to determine which antenna hastags thereon, thus reducing the time it takes to read all the antennason the roulette table.

However, using multiple antennas to cover an area presents new technicalchallenges. The multiple antennas magnetically couple and therebydistort the resulting magnetic field from the expected magnetic field,creating unwanted constructive interference (referred to as hot spots)and destructive interference (referred to as nulls). If the flux densityis too low, changes in the reflection coefficient when tags are placedin the in the low-flux area are undetectable and the fast scanningfeatures are unavailable. Section 3 discusses ways to increase the fluxdensity in large areas.

FIG. 8 is a top view of an antenna arrangement 800 that covers an areaon a gaming table. The antenna arrangement 800 includes two antennas 802and 804 that are coupled via a radio frequency switch 806 to othercomponents (not shown) such as a network analyzer, a RFID reader, etc.The antennas 802 and 804 are slightly overlapping in order to radiatethe field over the entirety of the area and to avoid a gap in coverage.The antenna arrangement 800 also has reactive elements that may includecapacitors and inductors. Here, the antenna arrangement 800 includes acapacitor 810 coupled to the antenna 802 in series, a capacitor 812coupled to the antenna 804 in series, and a capacitor 814 in a shuntconfiguration between the network analyzer and the switch 806. Thereactive elements may match the antennas 802 and 804 to 50 Ohms, whichis a common radio frequency design impedance, at 13.56 MHz.

For the antennas 802 and 804, considered by themselves in the absence ofthe other components, there is the potential for magnetic couplingbetween the antennas when the network analyzer measures the reflectioncoefficient. However, the placement of the shunt capacitor 814 on theopposite side of the switch 806 from the antennas 802 and 804 prevents aconductive loop from forming from one antenna (e.g. 802) through theother antenna (e.g. 804) to ground. (If a shunt element is placed on thesame side of the switch as the antenna, then the shunt element of oneantenna completes a connection to ground when the other antenna isenergized, resulting in magnetic coupling.) This placement of thereactive element on the opposite side of the switch from the antenna (oralternatively, on the same side of the switch as the network analyzer)may also be referred to as inboard placement.

The antenna arrangement 800 generally operates as follows. The antennas802 and 804 cover a betting spot on the roulette table, where thebetting spot is sized such that using a single, larger antenna wouldresult in a diminished flux density as discussed above. First, a networkanalyzer selectively measures the reflection coefficient of the antennas802 and 804; when the antenna 802 is measured, the switch 806 connectsthe antenna 802, and the antenna 804 is an open loop; when the antenna804 is measured, the switch 806 connects the antenna 804, and theantenna 802 is an open loop. When the quantity of chips that areenergized by a given antenna changes, the measured reflectioncoefficient changes from the previous reflection coefficient measurementfor the given antenna.

Second, based on comparing the measured reflection coefficients versusthe previous measurements, an RFID reader selectively energizes theantennas in the antenna arrangement 800 to perform a read operation.When the reflection coefficient for none of the antennas 802 and 804changes, no RFID read is needed because the current tags are the sametags that were present in the previous measurement. When the reflectioncoefficient for one of the antennas 802 and 804 changes, that particularantenna (e.g., 802) is connected via the switch 806 to the RFID reader,and the other antenna (e.g., 804) is an open loop; the RFID tags nearbythat particular antenna then respond with their tag identifiers to theread energy. When the reflection coefficient for both of the antennas802 and 804 changes, the switch 806 selectively connects the firstantenna (e.g. 802) for the RFID reader to energize, and makes an openloop for the second antenna (e.g. 804), then the switch 806 selectivelyconnects the second antennas (e.g. 804) for the RFID reader to energize,and makes an open loop for the first antenna (e.g. 802).

In summary, placing one or more reactive tuning elements inboard of theswitch 806 enables the use of any number of antennas to be used to covera defined area while maintaining the desired flux density. For example,the antennas may be selected from the antenna types listed in TABLE 2and used to provide coverage on areas of various dimensions on aroulette table.

FIG. 9 is a top view of an antenna arrangement 900 that covers an areaon a gaming table. The antenna arrangement 900 includes four antennas902, 904, 906 and 908 that are coupled via four radio frequency switches912, 914, 916 and 918 to other components (not shown) such as a networkanalyzer, a RFID reader, etc. The antennas 902, 904, 906 and 908 areslightly overlapping in order to radiate the field over the entirety ofthe area and to avoid a gap in coverage. The antenna arrangement 900also has reactive elements that may include capacitors and inductors.Here, the antenna arrangement 900 includes a capacitor 922 coupled inseries between the switch 912 and the antenna 902, a capacitor 924coupled in series between the switch 914 and the antenna 904, acapacitor 926 coupled in series between the switch 916 and the antenna906, and a capacitor 928 coupled in series between the switch 918 andthe antenna 908; and a capacitor 930 in a shunt configuration betweenthe network analyzer and the switches 912, 914, 916 and 918. Thereactive elements may match the antennas 902, 904, 906 and 908 to 50Ohms at 13.56 MHz. As with the antenna arrangement 800, using thecapacitor 930 as a shared (or common) shunt capacitor among the antennas902, 904, 906 and 908, and placing the capacitor 930 between the networkanalyzer and the switches 912, 914, 916 and 918, avoids magneticcoupling between the closely-placed antennas.

The antenna arrangement 900 may operate in a similar manner to theantenna arrangement 800 (see FIG. 8 ) discussed above.

FIG. 10 is a top view of an antenna arrangement 1000 that covers an areaon a gaming table. The antenna arrangement 1000 includes two figure-8antennas 1002 and 1004. Each of the antennas 1002 and 1004 is in afigure-8 shape with two loops (1002 a and 1002 b, and 1004 a and 1004b). The loops of the antennas 1002 and 1004 are slightly overlapping(e.g. the loop 1004 b overlaps the loops 1002 a and 1002 b) in order toradiate the field over the entirety of the area and to avoid a gap incoverage. Figure-8 antennas exhibit a null between the two loops. Thisnull area can be mitigated by spacing the loops such that the loop ofone antenna covers the null area of the other antenna. For example, theloop 1004 b covers the null of the antenna 1002, and the loop 1002 bcovers the null of the antenna 1004. The antennas 1002 and 1004 arecoupled via two radio frequency switches 1012 and 1014 to othercomponents (not shown) such as a network analyzer, a RFID reader, etc.

The antenna arrangement 1000 also has reactive elements that may includecapacitors and inductors. Here, the antenna arrangement 1000 includes acapacitor 1022 coupled in series between the switch 1012 and the antenna1002, and a capacitor 1024 coupled in series between the switch 1014 andthe antenna 1004; and a capacitor 1030 in a shunt configuration betweenthe network analyzer and the switches 1012 and 1014. The reactiveelements may match the antennas 1002 and 1004 to 50 Ohms at 13.56 MHz.As with the antenna arrangements 800 and 900, using the capacitor 1030as a shared (or common) shunt capacitor among the antennas 1002 and1004, and placing the capacitor 1030 between the network analyzer andthe switches 1012 and 1014, avoids magnetic coupling between theclosely-placed antennas.

The antenna arrangement 1000 may operate in a similar manner to theantenna arrangement 800 (see FIG. 8 ) or the antenna arrangement 900(see FIG. 9 ) discussed above.

FIG. 11 is a block diagram of an RFID system 1100. The RFID system 1100may be integrated into a roulette table (e.g. the roulette table 100 ofFIG. 1 ), in a manner similar to that described above regarding the RFIDsystem 200 (see FIG. 2 ), the RFID system 600 (see FIG. 6 ), the RFIDsystem 700 (see FIG. 7 ), etc. The RFID system 1100 generally implementsthe fast scanning features described above, and may include other of thefeatures described herein (e.g. Sections 1-2). The RFID system 1100includes a controller 1102, a network analyzer 1104, an RFID reader1106, a switchable reactance network 1108, and antennas 1110.

The controller 1102 generally controls the operation of the RFID system1100, for example by sending control signals to the network analyzer1104, the RFID reader 1106 and the switchable reactance network 1108, asdetailed below. The controller 1102 may be otherwise similar to thecontroller 202 (see FIG. 2 ), the controller 602 (see FIG. 6 ), thecontroller 706 (see FIG. 7 ), etc. The controller 1102 may beimplemented by a device that includes a processor, such as a personalcomputer.

The network analyzer 1104 measures a reflection coefficient of aselected one of the antennas 1110. Based on the reflection coefficient,the controller 1102 determines the approximate number of RFID tagspresent in the excitation field of the selected antenna and performsother operations. One such operation is configuring the switchablereactance network 1108 to an appropriate reactance value that matchesthe impedance of the selected antenna (because the RFID tags couple withthe selected antenna and change its impedance), as described in Section1 or Section 2. Another such operation is controlling the RFID reader1106 to perform a read operation on the selected antenna and to providethe detected RFID tag identifiers, so that the controller 1102 candetermine that specific RFID tags are present at the specific locationon the roulette table corresponding to the selected antenna. Because thenetwork analyzer generates results more quickly than the RFID reader1106, the controller 1102 may control the RFID reader 1106 to read onlythose of the antennas 1110 that have tags present (or that have a changein tag quantities), which results in a time savings as compared toalways reading all of the antennas 1110.

The RFID reader 1106 performs a read operation on the selected antennaof the antennas 1110. The read operation generally includes exciting theselected antenna, reading the responses of the RFID tags that respond tothe excitation energy, and providing the RFID tags identifiers of theresponding tags to the controller 1102. Because the controller 1102 hasconfigured the switchable reactance network 1108 to an appropriatereactance value based on the reflection coefficient measured by thenetwork analyzer 1104, the excitation energy is impedance matched to theselected antenna, and the read operation is performed more efficientlythan might otherwise occur. The RFID reader 1106 may be otherwisesimilar to the other RFID readers described herein, including the RFIDreader 204 (see FIG. 2 ), the RFID reader 606 (see FIG. 6 ), the RFIDreader 702 (see FIG. 7 ), etc.

The switchable reactance network 1108 generally selectively connects oneof the network analyzer 1104 and the RFID reader 1106 to a selectedantenna of the antennas 1110 with a selectable, a configurable or anadjustable reactance value. The controller 1102 configures theappropriate reactance value based on the reflection coefficient measuredby the network analyzer 1104. The switchable reactance network 1108includes reactive elements such as capacitors, inductors, etc. invarious series and shunt configurations. These various configurations ofreactive elements correspond to the range of impedances desired for thevarious types of antennas on the roulette table (see e.g. TABLE 2). Forexample, the switchable reactance network 1108 may implement the antennatunings described in Section 1, the dynamic antenna tunings described inSection 2, the specific capacitor arrangements of FIGS. 8-10 , etc.,including a number of radio frequency switches to connect the selectedantenna to the network analyzer 1104 (or the RFID reader 1106), and toconnect the selected reactance elements to the selected antenna.

The antennas 1110 are placed at various locations on the roulette table,for example the betting spots described above (see the roulette table100 of FIG. 1 and related text). The antennas 1110 have various types,for example the types listed in TABLE 2. The antennas 1110 may beotherwise similar to the antennas 208 (see FIG. 2 ), the antennas 612(see FIG. 6 ), the antennas 712 (see FIG. 7 ), the antennas 802 and 804(see FIG. 8 ), the antennas 902, 904, 906 and 908 (see FIG. 9 ), theantennas 1002 and 1004 (see FIG. 10 ), etc. A given area on the roulettetable may be associated with a single antenna (e.g., one of the antennatypes listed in TABLE 2), or with multiple antennas (e.g., as describedabove regarding FIGS. 8-10 ).

As a specific example regarding the antenna arrangement 1000 (see FIG.10 ), the controller 1102 controls the switchable reactance network 1108(in FIG. 10 , the switches 1012 and 1014, and the capacitors 1022, 1024and 1030) and the network analyzer 1104 to selectively measure thereflection coefficient of the antennas 1002 and 1004. If the reflectioncoefficient changes for the selected antenna from the previousmeasurement, that means the RFID tags at the betting spot have changed,so the controller 1102 controls the RFID reader 1106, via one switchconfiguration, to energize the selected antenna to perform a readoperation. The other antenna is selectively disconnected, via anotherswitch configuration, to form an open loop.

The RFID system 1110 may implement other features in addition to thefeatures described above. For example, the RFID reader 1106 mayimplement a persistence feature with the RFID tags. For persistence,when the RFID reader 1106 receives the identifier from a particular RFIDtag, the RFID reader 1106 instructs that particular RFID tag to nolonger respond during the current read operation. This allows the readcycle to proceed with no duplicate reads even if a tag is in anoverlapped region of the antennas 1110. For example, the antenna loops1002 a and 1004 b (see FIG. 10 ) are overlapping; an RFID tag located inthe overlapped area will be energized by both antennas 1002 and 1004.

As mentioned above, measuring the reflection coefficient of the antennas1110 (using the network analyzer 1104) prior to reading the RFID tags(using the RFID reader 1106) results in a time savings as compared tojust using the RFID reader 1106 to read all of the antennas 1110. Forexample, the average time for an operation of the network analyzer 1104is 0.3 milliseconds and for an operation of the RFID reader 1106 is 5milliseconds; for a roulette table with 200 antennas, using the RFIDreader 1106 to read all of the antennas 1110 takes 1000 milliseconds. Incontrast, using the network analyzer 1104 to measure the reflectioncoefficient of all the antennas takes 60 milliseconds; if the controller1102 determines that only 50 of the antennas 1110 need to be read(because the other 150 antennas do not have changed reflectioncoefficients), using the RFID reader 1106 to read that subset ofantennas takes only 250 milliseconds. The net time is then 310milliseconds (60+250), which is less than the 1000 milliseconds forreading all of the antennas 1110.

FIG. 12 is a flowchart of a method 1200 of determining locations ofobjects in a gaming environment. The method 1200 may be performed on theroulette table 100 (see FIG. 1 ) using the RFID system 1100 (see FIG. 11).

At 1202, a reflection coefficient of a selected antenna of a number ofantennas is measured. The antennas are arranged at a number of locationson a gaming table. For example, the roulette table 100 (see FIG. 1 ) mayhave a number of antennas (e.g. the types listed in TABLE 2) arranged todetect RFID tags at the various betting spots on the roulette table 100.At least some of the antennas are closely spaced, with multiple antennascovering a single betting spot, in order to fully cover the area whileproviding a desired flux density. The controller 1102 (see FIG. 11 ) maycontrol the network analyzer 1104 to measure the reflection coefficientof the selected antenna by configuring the connection to the selectedantenna through the switchable reactance network 1108.

At 1204, a reactance associated with the selected antenna is selectivelyadjusted based on the reflection coefficient having been measured (see1202). For example, the controller 1102 (see FIG. 11 ) may adjust thereactance of the switchable reactance network 1108 based on thereflection coefficient of the selected antenna measured by the networkanalyzer 1104. If the reflection coefficient for the selected antennahas not changed from its previous measurement, the reactance need not bechanged (e.g., selectively adjusted to remain unchanged). Because theantennas are closely spaced, the reactance adjustment uses an inboardshunt element in the switchable reactance network. For example, theswitchable reactance network 1108 may include an inboard shunt capacitor(e.g. on the same side of the switch as the network analyzer, or on theopposite side of the switch from the selected antenna), such as thecapacitor 814 (see FIG. 8 ), the capacitor 930 (see FIG. 9 ), thecapacitor 1030 (see FIG. 10 ), etc.

As a further option, the steps 1202-1204 may be performed more thanonce. For example, if a second measurement of the reflection coefficientindicates an impedance mis-match, the reactance may be further adjusted.

At 1206, when the reflection coefficient of the selected antenna haschanged from the previous measurement for the selected antenna, theselected antenna is energized, where energizing the selected antennaincludes energizing one or more RFID tags nearby the selected antennaand receiving one or more RFID tag identifiers from the one or more RFIDtags. For example, the RFID reader 1106 (see FIG. 11 ) may energize theselected antenna via the switchable reactance network 1108 using thereactance adjusted in 1204 to read the RFID tags in the vicinity of theselected antenna (e.g., the RFID tags located in a particular bettingspot on the roulette table that is associated with the selectedantenna). When the reflection coefficient has changed, this indicatesthat the RFID tags in the vicinity of the selected antenna have changed,so the RFID reader needs to perform a new read. However, when thereflection coefficient has not changed, this indicates that the RFIDtags in the vicinity of the selected antenna have not changed, so theRFID reader does not need to perform a read using the selected antenna.

At 1208, the first antenna is de-selected, a second antenna is selected,and the steps 1202, 1204 and 1206 are performed using the secondantenna.

The step 1208 may then be repeated for multiple antennas on the roulettetable (e.g., less than all of the antennas on the roulette table, asdetermined according to the changed reflection coefficients). Forexample, the controller 1102 (see FIG. 11 ) may control the RFID system1100 to selectively read the subset of the antennas 1110 that havechanged reflection coefficients from the reflection coefficientsmeasured in the previous read cycle. In this manner, the RFID system 200can determine the amount of bets placed at the various locations on theroulette table 100, without needing to perform a RFID read on all theantennas 1110.

In summary, the fast scanning features of Section 3 enable a number ofimprovements over existing systems. First, using multiple antennasprovides coverage over a larger area while avoiding coupling byselectively connecting one of the antennas and selectively disconnectingthe other antennas. This decoupling is performed by placing tuningcomponents outboard of the switch that is used for the selection.Second, using multiple antennas over the larger area maintains a definedflux density such that changes in the reflection coefficient when a RFIDtag is present in the excitation field are measureable (e.g., ascompared to using a single, larger antenna). Third, they result in timesavings by using the reflection coefficient to control which antennasthat the RFID reader reads (e.g. less than all of the antennas).

4. Instrumented Dolly

Section 4 describes an instrumented dolly that helps manage the gamestates in roulette. As mentioned above, a game of roulette may bearranged into three game states: Open Betting, Play, and Payout. Thegame logic is different for each game state. For example, bets areallowed to be placed or removed in the Open Betting state but not in thePlay state. The game also includes various events, such as the betslocked event, the winning number event, and the end of game event. Theevents mark the transition from one game state to another. Theinstrumented dolly described herein helps to accurately define thesetransitions.

A dolly is a standard part of roulette. Once the ball falls into aspecific slot on the wheel, the winning number is determined. In someembodiments, the winning number is sensed automatically; in otherembodiments, the croupier simply announces the winning number.

In either case (automated or not), the dolly is placed on the winningnumber on the roulette table, and it is not removed until all winningbets are paid.

The instrumented dolly described herein adds instrumentation to thedolly. Specifically, the instrumented dolly includes an RFID tag havinga unique identifier. This RFID-enabled dolly can then be used toautomatically detect these events and to trigger the use of new gamelogic for the subsequent game state. Specifically, the instrumenteddolly lives in one of two spots on the gaming table: On a dedicatedresting spot (referred to as “parked”), or on the winning number.

FIG. 13 is a block diagram of a RFID system 1300. The RFID system 1300may be integrated into a roulette table (e.g. the roulette table 100 ofFIG. 1 ), in a manner similar to that described above regarding the RFIDsystem 200 (see FIG. 2 ), the RFID system 600 (see FIG. 6 ), the RFIDsystem 700 (see FIG. 7 ), the RFID system 1100 (see FIG. 11 ), etc. TheRFID system 1300 generally implements the instrumented dolly featuresdescribed herein, and may include other of the features described herein(e.g. Sections 1-3). The RFID system 1300 includes a controller 1302, anRFID reader 1304, a switching network 1306, antennas 1308, and aninstrumented dolly 1310.

The controller 1302 generally controls the operation of the RFID system1300, for example by sending control signals to the RFID reader 1304 andthe switching network 1306, as detailed below. The controller 1302 alsomanages the game states described above according to the results ofdetecting the location of the instrumented dolly 1310. The controller1302 may be otherwise similar to the other controllers described herein,including the controller 202 (see FIG. 2 ), the controller 602 (see FIG.6 ), the controller 706 (see FIG. 7 ), the controller 1102 (see FIG. 11), etc. The controller 1302 may be implemented by a device that includesa processor, such as a personal computer.

The RFID reader 1304 performs a read operation on a selected antenna ofthe antennas 1308. The read operation generally includes exciting theselected antenna, reading the responses of the RFID tags that respond tothe excitation energy, and providing the RFID tags identifiers of theresponding tags to the controller 1302. Specifically regarding theinstrumented dolly 1310, the read operation reads the tag identifier ofthe instrumented dolly 1310 at the selected antenna, which correspondsto the betting spot with the winning number. The RFID reader 1304 may beotherwise similar to the other RFID readers described herein, includingthe RFID reader 204 (see FIG. 2 ), the RFID reader 606 (see FIG. 6 ),the RFID reader 702 (see FIG. 7 ), the RFID reader 1106 (see FIG. 11 ),etc.

The switching network 1306 generally connects the RFID reader 1304 to aselected antenna of the antennas 1308 using a plurality of switches. Theswitching network 1306 may also include a reactance network with aselectable, a configurable or an adjustable reactance value, similar tothe switchable reactance network 1108 (see FIG. 11 ). The switchingnetwork 1306 may be otherwise similar to the other switching networksdescribed herein, including the multiplexer 206 (see FIG. 2 ), themultiplexer 610 (see FIG. 6 ), the multiplexer 710 (see FIG. 7 ), theswitchable reactance network 1108, etc.

The antennas 1308 are placed at various locations on the roulette table,for example the betting spots described above (see the roulette table100 of FIG. 1 and related text). Specifically regarding the instrumenteddolly 1310, because the instrumented dolly 1310 is placed on the winningnumber in the 3×12 grid of numbers 1-36 (see FIG. 1 ), the antennas 1308correspond to the antennas in that area. One of the antennas 1308 mayalso be associated with the parking spot for the instrumented dolly1310. The antennas 1308 have various types, for example the types listedin TABLE 2 that are used in the 3×12 grid area of the roulette table.The antennas 1308 may be otherwise similar to the antennas 208 (see FIG.2 ), the antennas 612 (see FIG. 6 ), the antennas 712 (see FIG. 7 ), theantennas 802 and 804 (see FIG. 8 ), the antennas 902, 904, 906 and 908(see FIG. 9 ), the antennas 1002 and 1004 (see FIG. 10 ), the antennas1110 (see FIG. 11 ), etc.

The instrumented dolly 1310 contains a RFID tag that has a unique tagidentifier. When a read operation by the RFID reader 1304 returns thetag identifier of the instrumented dolly 1310 at a selected antenna ofthe antennas 1308 (e.g., as routed via the switching network 1306 asconfigured by the controller 1302), the controller 1302 recognizes thisas the winning number event and transitions the game state from the Playstate to the Payout state. Optionally, the controller 1302 may alsorecognize the bets locked event when the RFID reader 1304 detects thatthe instrumented dolly has been removed from the parking area.

The controller 1302 and the instrumented dolly 1310 generally interactas follows. With the instrumented dolly 1310 parked, the controllermaintains the game in the Open Betting state. Removing the instrumenteddolly 1310 from the parked location—in the absence of other automatedinputs—denotes the bets locked event. Placing the instrumented dolly1310 on a numbered spot on the roulette table defines the winning numberevent and denotes the transition to the Payout state. Removing theinstrumented dolly 1310 from the winning number defines the new gameevent, which represents the end of the Payout state and the transitionfrom the current game to the Open Betting state in the next game.

In some embodiments, the bets locked event is determined automatically(e.g. via a speed sensor in the wheel). In other embodiments, a manualaction by the dealer can define this event (e.g. the removal of theinstrumented dolly 1310 from the parked location). In some embodiments,the winning number is already known to the system (e.g. via a sensor inthe wheel). In other embodiments, placement of the instrumented dolly1310 in one of the 36 numbered areas in the 3×12 grid defines thewinning number. In other embodiments include both the sensor in thewheel and the detection of the instrumented dolly 1310 on the winningnumber, and the controller 1302 generates an alert if the results areinconsistent. Knowledge of the winning number determines which bets arewinners and which bets are losers. The controller 1302 may then use theinformation regarding the bets placed (e.g. according to the RFID tagsdetected at the various betting spots) and the winning number (e.g. bydetecting the RFID tag in the instrumented dolly 1310) to determine theproper payouts.

The instrumented dolly 1310 allows seamless integration with existinguse cases while providing exact timestamps for key events, triggeringchanges in the game state, and determining payouts. These featuresenable a wide range of novel metrics including win/loss calculations,player betting patterns (e.g. by associating particular RFID tags with aparticular player), dealer metrics (e.g. speed of play, number and typeof errors, etc.), and logging outcomes to determine if a wheel is“true”. These features also enable the controller 1302 to track variousalarms, such as a late bet alarm or a winning bet change alarm. The latebet alarm occurs when the system is in the bets locked state and any betoccurs (e.g. a change in the RFID tags detected at a particularantenna). The winning bet change alarm occurs when once the instrumenteddolly 1310 has been placed and winners and losers identified, the systementers the Payout state; the system detects any attempts to alter thebets placed on a winning spot and generates the alert.

In summary, the RFID system 1300 uses the RFID tag identifier of theinstrumented dolly 1310, which is read when the instrumented dolly 1310is placed on various locations on the roulette table, in order to changethe game state of the roulette game. This operation of the RFID system1300 differs from other uses of RFID tag identifers (e.g. to determinethe values of bets on a betting spot, to determine alerts, etc.) becausethese other uses are not used to change the game state. This operationof the RFID system 1300 also differs from other systems that change agame state because those systems use something other than a specificRFID tag identifier to change their game state.

5. Additional Applications

The features described above enable a number of additional applications,including a payout calculator and player win/loss correlation.

5.1. Payout Calculator

As noted above, roulette supports multiple bet types, each with its ownodds. Furthermore, players can win and lose simultaneously (e.g. byplacing bets on two numbers, only one of which is the winning number).And other players can make similar bets, with each bet distinguished bythe unique color of each player's chips. Thus, there is a need toimprove the accuracy and speed of payouts to winning bets.

The RFID system 1300 may track each bet using the antennas 1308 and theRFID reader 1304, determine the winning number using the instrumenteddolly 1301, and managing the game states using the controller 1302, andthe controller 1302 may use this information in combination with thepayout odds to calculate the proper payout for each bet. The controller1302 may display a payout calculator that shows the game state, theplayer chip colors and values, and for each player, the number of chipsto be paid out for winning bets, and the total value of the winningbets. This information helps to reduce errors and to speed up the game,both of which improve the casino's profitability.

5.2. Player Win/Loss Correlation

One goal of the embodiments described herein is to accurately reflectplayer loyalty with a well-defined metric based on actual facts. Buy insand cash outs are a staple of roulette, when the player exchanges theirvalue chips for color chips in order to place bets on the roulettetable. Signing in a player using their loyalty card is an attempt tounderstand how long a player remains at a table as a proxy for theirvalue as a customer, but time alone is a poor metric. Four additionalpieces of information are beneficial to generate a proper player loyaltymetric, including the color of their chips, the value they have assignedto their color chips, the size and type of their bets, and the playerwin/loss for each spin of the wheel.

Each of the systems described herein may bring together all five ofthese disparate data sets into a single player value metric that canresult in more efficient use of comps or other loyalty benefits. Knowingwhich colors, the value, the bet type and volume, and whether a playerwon or lost provides a definitive value of a player to a casino in theform of “Player X1 is worth $24.57/hour when he is at a roulette table”or “Player X1 has an account balance of $4,300 since May 1”.

Furthermore, by correlating player bets with wheel outcomes, the systemcan undertake long-term statistical analyses to determine whether thewheel is “true”, and if not true, do a player's betting patternscorrelate? If so, the system can generate an alert.

Enumerated Example Embodiments

Various aspects of the present invention may be appreciated from thefollowing enumerated example embodiments (EEEs).

EEE B 1. A system for determining locations of objects in a gamingenvironment, the system comprising: a plurality of radio-frequencyidentification (RFID) antennas arranged at a plurality of locations on agaming table; a RFID reader coupled to the plurality of RFID antennas; aplurality of reactive tuning components that couple the plurality ofRFID antennas to the RFID reader; and a controller, wherein thecontroller adjusts a reactance between the RFID reader and a selectedantenna of the plurality of RFID antennas, wherein adjusting thereactance includes selectively connecting one or more of the pluralityof reactive components, and wherein adjusting the reactance includesperforming impedance matching between the RFID reader and the selectedantenna.

EEE B2. The system of EEE B1, further comprising: a network analyzersystem, wherein the network analyzer system measures a reflectioncoefficient of the selected antennas, and wherein the controller adjuststhe reactance based on a result of measuring the reflection coefficient.

EEE B3. The system of EEE B2, wherein prior to each read operationperformed by the RFID reader, the network analyzer system measures thereflection coefficient and the controller adjusts the reactance of theplurality of reactive tuning components.

EEE B4. The system of EEE B2, wherein the plurality of RFID antennas hasa plurality of configurations, wherein each configuration includes oneof a plurality of turns and one of a plurality of loop sizes, whereinthe controller adjusts the reactance for each antenna of the pluralityof RFID antennas by switching a subset of the plurality of tuningcomponents, wherein the subset is selected according to the reflectioncoefficient measured for each antenna of the plurality of RFID antennas.

EEE B5. The system of EEE B1, wherein the RFID reader performs a firstread operation on the selected antenna, wherein the controller adjuststhe reactance based on a result of the first read operation, and whereinthe RFID reader performs a second read operation on the selected antennausing the reactance having been adjusted.

EEE B6. The system of EEE B1, wherein the plurality of reactive tuningcomponents includes a first set of components in a series configurationand a second set of components in a shunt configuration, wherein eachcomponent in a given set has a different reactance value from each othercomponent in the given set, and wherein the controller adjusts thereactance by selecting one or more of the first set of components andone or more of the second set of components.

EEE B7. The system of EEE B1, plurality of reactive tuning componentsincludes a plurality of pre-configured reactance configurations, whereinthe selected antenna is associated with a subset of the plurality ofpre-configured reactance configurations, and wherein the controlleradjusts the reactance by selecting one of the subset of the plurality ofpre-configured reactance configurations.

EEE B8. The system of EEE B1, wherein the RFID reader successivelyperforms a plurality of RFID read operations, wherein the controllerdynamically adjusts the reactance as the RFID reader successivelyperforms the plurality of RFID read operations.

EEE B9. A method of determining locations of objects in a gamingenvironment, the method comprising: providing a plurality ofradio-frequency identification (RFID) antennas arranged at a pluralityof locations on a gaming table; providing a RFID reader coupled to theplurality of RFID antennas; providing a plurality of reactive tuningcomponents that couple the plurality of RFID antennas to the RFIDreader; and adjusting a reactance between the RFID reader and a selectedantenna of the plurality of RFID antennas, wherein adjusting thereactance includes selectively connecting one or more of the pluralityof reactive components, and wherein adjusting the reactance includesperforming impedance matching between the RFID reader and the selectedantenna.

EEE C1. A system for determining locations of objects in a gamingenvironment, the system comprising: a plurality of radio-frequencyidentification (RFID) antennas arranged at a plurality of locations on agaming table; a network analyzer system; an RFID reader; a switchablereactance network that selectively connects the plurality of RFIDantennas with one of the network analyzer system and the RFID readerusing a selectable reactance, wherein the switchable reactance networkincludes a plurality of switches and a shunt element, wherein the shuntelement is located inboard of at least two of the plurality of switches;and a controller, wherein the controller controls the network analyzersystem to measure a reflection coefficient of a selected antenna of theplurality of RFID antennas, and wherein based on the reflectioncoefficient having been measured, the controller controls the RFIDreader to energize the selected antenna, wherein in response toenergizing the selected antenna, the RFID reader receives at least oneRFID tag identifier from at least one RFID tag near the selectedantenna.

EEE C2. The system of EEE C1, wherein the plurality of RFID antennasincludes two or more antennas arranged to cover a given area of thegaming table, wherein the controller selectively couples the networkanalyzer system to each of the two or more antennas to measure areflection coefficient of each of the two or more antennas, whereinselectively coupling includes selectively connecting each one of the twoor more antennas and selectively disconnecting, via an open loop, allother of the two or more antennas besides the one antenna that has beenselectively connected, and wherein the controller controls the RFIDreader to selectively energize the two or more antennas based on aresult of measuring the reflection coefficient of each of the two ormore antennas.

EEE C3. The system of EEE C1, wherein the controller controls theswitchable reactance network to connect one of the network analyzersystem and the RFID reader to the selected antenna using the pluralityof switches.

EEE C4. The system of EEE C1, wherein the controller controls theswitchable reactance network to adjust the selectable reactance based onthe reflection coefficient having been measured.

EEE C5. A method of determining locations of objects in a gamingenvironment, the method comprising: providing a plurality ofradio-frequency identification (RFID) antennas arranged at a pluralityof locations on a gaming table; providing a network analyzer system;providing an RFID reader; providing a switchable reactance network thatselectively connects the plurality of RFID antennas with one of thenetwork analyzer system and the RFID reader using a selectablereactance, wherein the switchable reactance network includes a pluralityof switches and a shunt element, wherein the shunt element is locatedinboard of at least two of the plurality of switches; controlling thenetwork analyzer system to measure a reflection coefficient of aselected antenna of the plurality of RFID antennas; and based on thereflection coefficient having been measured, controlling the RFID readerto energize the selected antenna, wherein in response to energizing theselected antenna, the RFID reader receives at least one RFID tagidentifier from at least one RFID tag near the selected antenna.

EEE D1. A system for determining locations of objects in a gamingenvironment, the system comprising: a plurality of radio-frequencyidentification (RFID) antennas arranged at a plurality of locations on agaming table; a RFID reader coupled to the plurality of RFID antennas;an instrumented dolly having an RFID tag; and a controller, wherein thecontroller manages a plurality of game states related to the gamingtable, wherein the RFID reader reads the instrumented dolly based on aproximity of the instrumented dolly to a subset of the plurality of RFIDantennas on the gaming table, wherein the subset is less than all of theplurality of RFID antennas, and wherein the controller changes from oneof the plurality of game states to another of the plurality of gamestates based on a result of the RFID reader reading the instrumenteddolly.

EEE D2. The system of EEE D1, wherein the plurality of game statesincludes an Open Betting state, a Play state, and a Payout state.

EEE D3. The system of EEE D1, wherein the result of the RFID readerreading the instrumented dolly corresponds to one of a plurality ofevents, wherein the plurality of events includes a bets locked event, awinning number event, and a new game event.

EEE D4. The system of EEE D1, wherein the RFID reader reads a pluralityof RFID tags nearby the plurality of RFID antennas, and wherein thecontroller generates an alert based on a current game state of theplurality of game states and a change in the plurality of RFID tags.

EEE D5. The system of EEE D1, wherein the gaming table includes aninstrumented wheel that determines a winning number, wherein thecontroller determines a winning number by detecting the instrumenteddolly by a particular antenna of the plurality of RFID antennas, andwherein the controller generates an alert when the winning numberdetermined by detecting the instrumented dolly differs from the winningnumber determined by the instrumented wheel.

EEE D6. A method of determining locations of objects in a gamingenvironment, the method comprising: providing a plurality ofradio-frequency identification (RFID) antennas arranged at a pluralityof locations on a gaming table; providing a RFID reader coupled to theplurality of RFID antennas; providing an instrumented dolly having anRFID tag; managing, by a controller, a plurality of game states relatedto the gaming table; reading, by the RFID reader, the instrumented dollybased on a proximity of the instrumented dolly to a subset of theplurality of RFID antennas on the gaming table, wherein the subset isless than all of the plurality of RFID antennas; changes, by thecontroller, from one of the plurality of game states to another of theplurality of game states based on a result of the RFID reader readingthe instrumented dolly.

The above description illustrates various embodiments of the presentinvention along with examples of how aspects of the present inventionmay be implemented. The above examples and embodiments should not bedeemed to be the only embodiments, and are presented to illustrate theflexibility and advantages of the present invention as defined by thefollowing claims. Based on the above disclosure and the followingclaims, other arrangements, embodiments, implementations and equivalentswill be evident to those skilled in the art and may be employed withoutdeparting from the spirit and scope of the invention as defined by theclaims.

What is claimed is:
 1. A system for determining locations of objects ina gaming environment, the system comprising: a plurality ofradio-frequency identification (RFID) antennas arranged at a pluralityof locations on a gaming table; a RFID reader coupled to the pluralityof RFID antennas; a plurality of reactive tuning components that couplethe plurality of RFID antennas to the RFID reader; and a controller,wherein the controller adjusts a reactance between the RFID reader and aselected antenna of the plurality of RFID antennas, wherein adjustingthe reactance includes selectively connecting one or more of theplurality of reactive components, and wherein adjusting the reactanceincludes performing impedance matching between the RFID reader and theselected antenna.
 2. The system of claim 1, further comprising: anetwork analyzer system, wherein the network analyzer system measures areflection coefficient of the selected antennas, and wherein thecontroller adjusts the reactance based on a result of measuring thereflection coefficient.
 3. The system of claim 2, wherein prior to eachread operation performed by the RFID reader, the network analyzer systemmeasures the reflection coefficient and the controller adjusts thereactance of the plurality of reactive tuning components.
 4. The systemof claim 2, wherein the plurality of RFID antennas has a plurality ofconfigurations, wherein a given configuration includes a given numberturns and a given loop size, wherein the controller adjusts thereactance for each antenna of the plurality of RFID antennas byswitching a subset of the plurality of tuning components, wherein thesubset is selected according to the reflection coefficient measured foreach antenna of the plurality of RFID antennas.
 5. The system of claim1, wherein the RFID reader performs a first read operation on theselected antenna, wherein the controller adjusts the reactance based ona result of the first read operation, and wherein the RFID readerperforms a second read operation on the selected antenna using thereactance having been adjusted.
 6. The system of claim 1, wherein theplurality of reactive tuning components includes a first set ofcomponents in a series configuration and a second set of components in ashunt configuration, wherein each component in a given set has adifferent reactance value from each other component in the given set,and wherein the controller adjusts the reactance by selecting one ormore of the first set of components and one or more of the second set ofcomponents.
 7. The system of claim 1, wherein the plurality of reactivetuning components includes a plurality of pre-configured reactanceconfigurations, wherein the selected antenna is associated with a subsetof the plurality of pre-configured reactance configurations, and whereinthe controller adjusts the reactance by selecting one of the subset ofthe plurality of pre-configured reactance configurations.
 8. The systemof claim 1, wherein the RFID reader successively performs a plurality ofRFID read operations, wherein the controller dynamically adjusts thereactance as the RFID reader successively performs the plurality of RFIDread operations.
 9. The system of claim 1, wherein the controlleradjusts a reactance between the RFID reader and a selected one or moreof the plurality of antennas.
 10. A method of determining locations ofobjects in a gaming environment, the method comprising: providing aplurality of radio-frequency identification (RFID) antennas arranged ata plurality of locations on a gaming table; providing a RFID readercoupled to the plurality of RFID antennas; providing a plurality ofreactive tuning components that couple the plurality of RFID antennas tothe RFID reader; and adjusting a reactance between the RFID reader and aselected antenna of the plurality of RFID antennas, wherein adjustingthe reactance includes selectively connecting one or more of theplurality of reactive components, and wherein adjusting the reactanceincludes performing impedance matching between the RFID reader and theselected antenna.
 11. The method of claim 10, further comprising:providing a network analyzer system; and measuring, by the networkanalyzer system, a reflection coefficient of the selected antennas,wherein adjusting the reactance includes adjusting the reactance basedon a result of measuring the reflection coefficient.
 12. The method ofclaim 11, wherein prior to each read operation performed by the RFIDreader, the network analyzer system measures the reflection coefficient,and the reactance of the plurality of reactive tuning components isadjusted
 13. The method of claim 11, wherein the plurality of RFIDantennas has a plurality of configurations, wherein a givenconfiguration includes a given number of turns and a given loop size,wherein adjusting the reactance for each antenna of the plurality ofRFID antennas includes switching a subset of the plurality of tuningcomponents, wherein the subset is selected according to the reflectioncoefficient measured for each antenna of the plurality of RFID antennas.14. The method of claim 10, wherein the RFID reader performs a firstread operation on the selected antenna, adjusting the reactance includesadjusting the reactance based on a result of the first read operation,and wherein the RFID reader performs a second read operation on theselected antenna using the reactance having been adjusted.
 15. Themethod of claim 10, wherein the plurality of reactive tuning componentsincludes a first set of components in a series configuration and asecond set of components in a shunt configuration, wherein eachcomponent in a given set has a different reactance value from each othercomponent in the given set, and wherein adjusting the reactance includesselecting one or more of the first set of components and one or more ofthe second set of components.
 16. The method of claim 10, wherein theplurality of reactive tuning components includes a plurality ofpre-configured reactance configurations, wherein the selected antenna isassociated with a subset of the plurality of pre-configured reactanceconfigurations, and wherein adjusting the reactance includes selectingone of the subset of the plurality of pre-configured reactanceconfigurations.
 17. The method of claim 10, wherein the RFID readersuccessively performs a plurality of RFID read operations, whereinadjusting the reactance includes dynamically adjusting the reactance asthe RFID reader successively performs the plurality of RFID readoperations.
 18. An apparatus for determining locations of objects in agaming environment, the apparatus comprising: a gaming table; aplurality of radio-frequency identification (RFID) antennas arranged ata plurality of locations on the gaming table; a RFID reader coupled tothe plurality of RFID antennas; a plurality of reactive tuningcomponents that couple the plurality of RFID antennas to the RFIDreader; and a controller, wherein the controller adjusts a reactancebetween the RFID reader and a selected antenna of the plurality of RFIDantennas, wherein adjusting the reactance includes selectivelyconnecting one or more of the plurality of reactive components, andwherein adjusting the reactance includes performing impedance matchingbetween the RFID reader and the selected antenna.
 19. The apparatus ofclaim 18, further comprising: a network analyzer system, wherein thenetwork analyzer system measures a reflection coefficient of theselected antennas, and wherein the controller adjusts the reactancebased on a result of measuring the reflection coefficient.
 20. Theapparatus of claim 18, wherein the RFID reader performs a first readoperation on the selected antenna, wherein the controller adjusts thereactance based on a result of the first read operation, and wherein theRFID reader performs a second read operation on the selected antennausing the reactance having been adjusted.